Field of the Invention
The present invention relates to an ejector arranged to flow working fluid to generate negative pressure and cause target fluid to flow by action of the negative pressure.
Related Art
As the above type of technique, heretofore, there is known a jet pump (an ejector) used in a blow-by gas returning device disclosed for example in Patent Document 1 listed below. This blow-by gas returning device is mounted in an engine including a supercharger in an intake passage and configured to return or recirculate blow-by gas generated in the engine to the intake passage through a blow-by gas returning passage. This returning device includes a bypass passage connecting an upstream portion and a downstream portion of the intake passage with respect to the supercharger, and an ejector for generating negative pressure in the bypass passage. An exit of the blow-by gas returning passage is connected to the bypass passage via the ejector. Accordingly, during operation of the supercharger, a pressure difference of intake air occurs between the upstream side and the downstream side of the supercharger in the intake passage and also between both ends of the bypass passage. By this pressure difference, air is caused to flow as working fluid in the bypass passage, thereby generating negative pressure in the ejector. By action of this negative pressure, blow-by gas is caused to flow as target fluid into the ejector through the blow-by gas returning passage, and then flow to the intake passage through the bypass passage.
In the above returning device, as the supercharging pressure by the supercharger rises, the air flow rate in the bypass passage, that is, the amount of air allowed to flow in the ejector increases, so that the negative pressure generated in the ejector becomes higher. Accordingly, the flow rate of blow-by gas caused to flow to the intake passage via the blow-by gas returning passage, ejector, and bypass passage increases with a rise in supercharging pressure.